Background: Frozen shoulder is characterized with thickening and contracture of joint capsular. The mechanism of this disorder is not yet clear, however, some proteins have been related to frozen shoulder. This study was to compare the serum levels of proteins related to frozen shoulder, such as matrix metalloproteinase (MMP), tissue inhibitor of metalloproteinase (TIMP) and transforming growth factor-beta (TGF-β) between frozen shoulder and normal subjects; and before and after physical exercise active stretching and gentle thawing in frozen shoulder patients. Methods: Serum levels of MMP-1, MMP-2, TIMP-1, TIMP-2, and TGF-β1 was measured from frozen shoulder and normal subjects by using ELISA. Functional assessment of shoulder joint in frozen shoulder patients was based on abbreviated Constant score. Frozen shoulder patients were randomly divided into intensive stretching and supervised neglect groups. Abbreviated Constant score and serum samples of frozen shoulder patients were evaluated at baseline, week-6, and week-12 after exercise, while only baseline serum samples of control were measured. MMP/TIMP ratio was calculated from the total sum of MMP-1 and MMP-2 levels divided by the total sum of TIMP-1 and TIMP-2 levels. Results: Baseline MMP-1 and MMP-2 levels were significantly lower, while TIMP-1, TIMP-2, and TGF-β1 levels were significantly higher in frozen shoulder group than in control. Increased MMPs and decreased TIMPs were significantly greater after intensive stretching than after supervised neglect exercise. Abbreviated Constant score improvement was significantly higher in intensive stretching group than in supervised neglect group. Conclusions: Serum levels of MMP-1, MMP-2, TIMP-1, TIMP-2, and TGF-β1 may be associated to frozen shoulder. Active stretching can improve frozen shoulder better than supervised neglect, as demonstrated by the improvement of Constant score.